An apparatus and method of rolling the outer fillets of split pin crankshafts by having tools rubbing together to absorb opposing forces are disclosed in Hegenscheidt's U.S. Pat. Nos. 5,575,167 and 5,445,003. The problem with this method using conventional single roller rolling tools is that because the split pins are on different centerlines, the opposing forces of the single fillet rollers cause the tools and rolling arms to twist, which in turn cause separation and excessive wear on the wear plates or friction devices between the tools.
More specifically, U.S. Pat. No. 5,575,167 discloses and illustrates in FIG. 6 non-adjacent fillets of adjacent split pins, i.e. the outer fillets of the adjacent split pins, which are rolled at a pressure by inclined work rollers. The rollers are mounted on adjacent tool heads to project out from the lower ends thereof. Each tool housing is mounted to an upper arm of a pair of scissor arms with the tool housing for the back-up rollers mounted to the lower arm. Accordingly, when the arms are shifted for clamping the rollers on the pin fillets, the lower projecting work roller of the upper arm tool housing will engage on the upper side of the fillet with the upwardly projecting pair of back-up rollers engaging on the lower side of the pin bearing, outside of the fillet area.
The arms are next to each other so that their tool heads are placed side-by-side during the rolling process. The opposing tool housings of the work rollers have a central bearing unit mounted therebetween to lessen the friction due to the opposing side loads generated during the simultaneous rolling of a pair of outer fillets of the split pin bearings. The central bearing unit is said to spread the side loads while allowing the housing of the tool heads to easily move relative to one another during rolling. As illustrated in FIG. 5 of this patent, a pair of backup rollers are provided on a tool arm disposed opposite the tool arm carrying a single operative working roller which imparts the rolling forces to roll harden the fillet. Because the adjacent pin bearings have axes which are offset to each other for the split bearing and with the working rollers and backup rollers positioned in this manner, the tool heads and/or the tool arms tend to bend or twist from a true vertical plane which results in undue stress and premature wear of both the rolling tool heads and the rolling arms. In production equipment where flat surfaces on the rolling tools or housings, which are supposed to rub together, try instead to separate, this action causes high wear in certain areas and premature failure.
More specifically, FIGS. 8A and 8B and 9A and 9B herein illustrates the prior art, as disclosed in FIG. 6 of U.S. Pat. No. 5,575,167, wherein a single working roller 94 is provided on each tool 70, 72 engaging split pin bearing fillets 95 and 97. Referencing the '167 patent, a pair of backup rollers 98 are carried on a tool 74, 76 on a second tool arm 80, and the single working roller 94 is carried on a first tool arm 78. When the left crank pin bearing is in its upper vertical position (FIG. 8A), there is generally a counterclockwise sideways force c about a horizontal axis normal to the crankshaft axis. When the right pin bearing is located in its upper vertical position (FIG. 8B), an oppositely directed clockwise sideways force c exists. When the left crank pin bearing is horizontal, as shown in FIG. 9A, a counterclockwise sideways force c about a vertical axis is generated. An opposite clockwise sideways force c is generated when the crankshaft has rotated 180° from FIG. 9B. These sideway forces c cause unwanted movements of the tool heads and the tool arms that can result in premature failure and high wear in certain areas.
In Ingersoll's U.S. Pat. No. 6,895,793, which is incorporated by reference as if reproduced in its entirety herein, there is disclosed a very thin rolling arm which carries both a single working roller and a pair of support rollers. It would be desirable to use the thin arms to roll split pin bearings. However, due to the large side forces exerted upon them during the rolling of the outer fillets of the split bearings of the crankshaft, the rolling tool arms will want to rock side-to-side in both the vertical and the horizontal positions of the pin bearing because the forces are consistently changing direction from side-to-side with each 180° rotation of the crankshaft, as explained above in connection with FIGS. 8 and 9 herein.